1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to an LCD device with good transmittance.
2. Discussion of the Related Art
A liquid crystal display (LCD) device may be widely used in various fields of notebook computer, monitor, spacecraft, aircraft, and etc. owing to advantages of low driving voltage, low power consumption and portability.
The LCD device includes a lower substrate, an upper substrate, and a liquid crystal layer between the lower and upper substrates. Liquid crystal molecules in the liquid crystal layer are aligned according to an application of electric field, whereby light transmittance is adjusted based on the alignment of liquid crystal molecules, to thereby display images on the LCD device.
Hereinafter, a related art LCD device will be described with reference to the accompanying drawings.
FIG. 1A is a cross section view illustrating a related art LCD device.
As shown in FIG. 1A, the related art LCD device includes a lower substrate 10, an upper substrate 20, and a liquid crystal layer (not shown) between the lower and upper substrates 10 and 20.
The lower substrate 10 comprises a lower base 11 and a device layer 12, wherein the device layer 12 is formed on the lower base 11. The device layer 12 may comprise a thin film transistor, a pixel electrode, and a common electrode.
The upper substrate 20 comprises an upper base 21; light-shielding layers 22; red (R), green (G), and blue (B) color filter layers 24; and an overcoat layer 26. In this case, the light-shielding layers 22 are formed on the upper base 21; the red (R), green (G), and blue (B) color filter layers 24 are respectively formed between each of the light-shielding layers 22; and the overcoat layer 26 is formed on the color filter layers 24.
The related art LCD device comprises plural pixels, wherein each pixel is capable of realizing various colors by combining red (R)-colored sub-pixel (SPR), green (G)-colored sub-pixel (SPG), and blue (B)-colored sub-pixel (SPB).
However, a cell gap (DR) of the red (R)-colored sub-pixel (SPR), a cell gap (DG) of the green (G)-colored sub-pixel (SPG), and a cell gap (DB) of the blue (B)-colored sub-pixel (SPB) are the same in the related art LCD device. Thus, there are limits to improvement of transmittance. This will be explained in detail as follows.
FIG. 1B is a graph illustrating the change in light transmittance for each color according to the cell gap. As shown in FIG. 1B, according as the cell gap increases, the red (R)-colored light transmittance and green (G)-colored light transmittance are gradually increased, and are then decreased. Meanwhile, the blue (B)-colored light transmittance is gradually decreased together with the increase of cell gap.
As known from the related art LCD device, when the cell gap (DR) of the red (R)-colored sub-pixel (SPR), the cell gap (DG) of the green (G)-colored sub-pixel (SPG), and the cell gap (DB) of the blue (B)-colored sub-pixel (SPB) are the same, it is difficult to maximize the transmittance for each of the colored light.
That is, in case of the related art, the cell gaps (DR, DG, DB) of all sub-pixels are set to be identical with respect to the point where the green (G)-colored light transmittance is high. In this case, the red (R)-colored light and blue (B)-colored light transmittances are relatively lowered so that the entire transmittance of the LCD device is also lowered.